In offline power supplies, current and voltage slew rates are preferably slow to reduce the EMI (electro-magnetic interference) filter size so that system cost is minimized. However, slow current and voltage slew rates make the system slow to react. For example, if a high voltage surge event such as lighting, inductive voltage kick or any form of high voltage spikes from other sources happens, the system may not react quickly enough to prevent it from being destructed due to the slow reaction.